Here, the term workpiece refers to a single component or to an assembly consisting of two interlocked components.
The circumferential processing can be, for example, the welding of two plastic components, the shrinking of a film tube onto a glass fiber, or the curing of a coating on a component.
Devices of this generic type can be found in the state of the art especially in conjunction with welding processes. A distinction is made here between contour welding and simultaneous welding.
In contour welding, one or more laser beams and a workpiece that is to be welded are moved relative to each other so that the laser beam or beams pass over the workpiece circumferential surface along a desired weld seam.
In simultaneous welding, the entire weld seam is exposed to one or more laser beams at the same time.
U.S. Pat. No. 7,368,681 B2 describes such a device. It comprises a plurality of laser beam sources which are arranged at equal distances from each other on a circle and which each emit a laser beam radially with respect to the mid-point of the circle where the laser beams are superimposed and are supposed to form a processing area having a constant energy density. A beam-forming lens system, which influences the divergence of the laser beams, is arranged in front of the laser sources, which can be diode lasers (laser diodes or laser diode bars), as seen in the radiation direction.
In this process, via the divergence in the plane of the circle, in conjunction with the radius of the circle, the size of the processing area having a constant energy density can be adapted to the size of the workpiece that is placed into this processing area in order to be processed. The beam expansion perpendicular to the plane of the circle is the determining factor for the width of the weld seam.
Since the energy distribution in a laser beam fundamentally corresponds to a Gaussian distribution, the homogeneity of the energy distribution improves with the increasing number of superimposed laser beams that are offset with respect to each other.
A drawback is that an approximately constant energy density in the plane of the circle, which is the determining factor for the quality of the weld seam along its length, is only achieved with a very large number of laser beam sources.
The energy distribution perpendicular to the plane, which is the determining factor for the quality of the weld seam along its width, still remains a Gaussian distribution.
Moreover, such a device calls for additional measures that ensure the laser safety, i.e. ensuring that neither people nor machines are exposed to the risk of injury or damage by the laser beams while the device is operational.